7,877 research outputs found
Time-dependent toroidal compactification proposals and the Bianchi type I model: classical and quantum solutions
In this work we construct an effective four-dimensional model by
compactifying a ten-dimensional theory of gravity coupled with a real scalar
dilaton field on a time-dependent torus. This approach is applied to
anisotropic cosmological Bianchi type I model for which we study the classical
coupling of the anisotropic scale factors with the two real scalar moduli
produced by the compactification process. Under this approach, we present an
isotropization mechanism for the Bianchi I cosmological model through the
analysis of the ratio between the anisotropic parameters and the volume of the
Universe which in general keeps constant or runs into zero for late times. We
also find that the presence of extra dimensions in this model can accelerate
the isotropization process depending on the momenta moduli values. Finally, we
present some solutions to the corresponding Wheeler-DeWitt (WDW) equation in
the context of Standard Quantum Cosmology.Comment: LaTeX source, 16 pages, Modified title and additional references.
Advances in High Energy Physics, 201
Role of resonances in rho^0 -> pi^+ pi^- gamma
We study the effect of the sigma(600) and a_1(1260) resonances in the rho^0
-> pi^+ pi^- gamma decay, within the meson dominance model. Major effects are
driven by the mass and width parameters of the sigma(600), and the usually
neglected contribution of the a_1(1260), although small by itself, may become
sizable through its interference with pion bremsstrahlung, and the proper
relative sign can favor the central value of the experimental branching ratio.
We present a procedure, using the gauge invariant structure of the resonant
amplitudes, to kinematically enhance the resonant effects in the angular and
energy distribution of the photon. We also elaborate on the coupling constants
involved.Comment: 5 pages, 5 figures, accepted for publication in PR
Enhancement of Epidemiological Models for Dengue Fever Based on Twitter Data
Epidemiological early warning systems for dengue fever rely on up-to-date
epidemiological data to forecast future incidence. However, epidemiological
data typically requires time to be available, due to the application of
time-consuming laboratorial tests. This implies that epidemiological models
need to issue predictions with larger antecedence, making their task even more
difficult. On the other hand, online platforms, such as Twitter or Google,
allow us to obtain samples of users' interaction in near real-time and can be
used as sensors to monitor current incidence. In this work, we propose a
framework to exploit online data sources to mitigate the lack of up-to-date
epidemiological data by obtaining estimates of current incidence, which are
then explored by traditional epidemiological models. We show that the proposed
framework obtains more accurate predictions than alternative approaches, with
statistically better results for delays greater or equal to 4 weeks.Comment: ACM Digital Health 201
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